Sony HB-F1XV video issues (and cut traces)

By fallen1

Supporter (4)

fallen1's picture

10-10-2019, 03:09

Hi, I got a HB-F1XV from Japan and I've connected it via shielded DIN8->Scart cable to OSSC but with very bad picture quality (horizontal bars scrolling upwards) and no output on the RCA connectors.
I was afraid that there is damage from leaking, but after opening it, the daughterboard (HIC1) capacitors were already replaced by thru-hole caps with very little corrosion damage:
https://drive.google.com/open?id=1nkdlN_BXhJ2fX_PYE4KWQjUina...

So I got the whole board out to see the bottom part and it seems that someone has cut all the GND traces to the RCA connectors. I don't see any jumper cables so I don't think it's any kind of mod - just some sort of damage mitigation (the HIC1 daughter board looks like it was taken out and put back - maybe for the recap).
https://drive.google.com/open?id=1A7C40ywhzeqebXKR9w7tuOiRhq...

Does anyone know what could be the reason why those traces were cut?
Should I repair the cut traces? Will it solve my screen issues? How can I fix the bars ( sorry no photo, my step-down transformer is blown and waiting for new one...)

Thank you

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By Alexey

Guardian (2349)

Alexey's picture

10-10-2019, 12:19

What an ugly job! Probably someone wanted to verify whether the interference came from the ground, cut the traces and took the ground from a different place. When that didn't work, he replaced the caps, but forgot to repair the cuts. Try to take the video ground from the other side of the cut track and also from a different location on the motherboard. If it makes no difference to the picture, I think repairing the cuts will resolve your video problem.

By fallen1

Supporter (4)

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10-10-2019, 18:59

Thank you for your response.

Connected the cut traces so there is connectivity at RCA to ground now, but still no video output (continuity is ok between the RCA video signal and the HIC1 daughterboard's video pin) - the RGB remained noisy
I tried to replace all 4 RGB+Sync capacitors between the HIC1 and DIN (used Panasonic), but again no change - at least I made a video this time (it does this on OSSC/no OSCC and two different monitors. I re-did the cable too + added 2 ferrite cores): https://drive.google.com/file/d/1zk-a7MzOprmL31UQ3fFQKKXiQ6a...

Do you have any idea what to try next? Recap all?

Thank you!

ps: Learned my lesson. "untested, powers on" means "tried to repair, butchered the board but LED still works" ...

By Meits

Scribe (5487)

Meits's picture

10-10-2019, 21:37

Go here (the XV's older sister, but practically the same). See if there's something you might check. One brand of caps is very inferior. If you have them, it wouldn't hurt replacing them. When seeing the pictures, take in consideration that the mainboard looked mint little over a year earlier.
It might still be wise to remove the remaining corrosion on the hic.

By fallen1

Supporter (4)

fallen1's picture

11-10-2019, 10:50

Ok, thanks for the link - so I'll try to replace rest of the electrolytic caps and then test again.
Will this be a sync related problem?

By Meits

Scribe (5487)

Meits's picture

11-10-2019, 11:35

That I do not know, but if you've got the Elna caps on your board, they're suspect of being dead/dying, so while you're at it Wink

By fallen1

Supporter (4)

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14-10-2019, 11:22

Ok, stupid me managed to kill the MSX Sad

Backstory: the HIC had a wiggle that was shutting off the RGB (most likely due corrosion), so I reflowed the ICs and when trying wiggling again, it just went black (and never got back...).

So I borrowed an oscillator and this is what I found out so far:
- Black screen
- power + turbo led on
- no activity on the speed led (there was activity before the accident)
- no capslock response
- power on cpu, vdp, hic ok
- HIC (26) sync signal ok, nothing on HIC RGB IN, same on V9958 (no RGB output signals)

So it seems the V9958 is busted - so I checked the datasheet at http://map.grauw.nl/resources/video/yamaha_v9958_ocr.pdf

So I have lot of questions now:

  • Did I interpret the above readings correctly?
  • Is there a safe way to exclude the "S-1985 MSX2 SYSTEM" IC from the equation?
  • Should I socket the V9958? There is the analog RGB so I think it would decrease the signal quality (once I get other then black color :)